An astrophysicist, Riess was a leader in discovering
that dark energy, a mysterious and still
unexplained force, is driving the universe to expand at an
ever-faster rate, overcoming the effects of
gravity. He was first author on a paper published in 1998
by one of two competing groups of scientists
that made the discovery; his innovative approach involved
comparisons of the "redshift" of rare Type
Ia supernovas spotted at varying distances from Earth in
the farthest reaches of space.

Riess has shared two of cosmology's most prestigious
prizes — the 2006 Shaw Prize and the
Peter Gruber Foundation's 2007 Cosmology Prize — for
this discovery, and last year he was a recipient
of a John D. and Catherine T. MacArthur Foundation
Fellowship, often called a "genius grant."

A 2003 National Academy of Sciences report referred to
the nature of dark energy as "the
deepest mystery in physics" and said that "its resolution
is likely to greatly advance our understanding
of matter, space and time."

Riess and his colleagues at Johns Hopkins and at the
Space Telescope Science Institute, where
Riess has been an astronomer since 1999, are working to
learn more using the
Hubble Space Telescope
and ground-based experiments. For example, in 2003 Riess
announced results from Hubble
observations of Type 1a supernovae, which suggested that 5
billion years ago a transition occurred
between a time when gravity put the "brakes" on universal
expansion and a time when dark energy
dominated and began to accelerate the universe's
expansion.

Adam Falk, the James B. Knapp Dean of the Krieger
School, says that Riess' work has done
nothing less than "revolutionize" our understanding of the
past and future of space and time.

"It is not an exaggeration to say that his discovery
of the acceleration of the expansion of the
universe was one of the great discoveries of the 20th
century," Falk said. "It has completely re-
oriented both cosmology and high-energy physics. We are
very proud to have Adam at Johns Hopkins."

Riess is a 1992 graduate of MIT and earned a doctorate
in 1996 from Harvard. From 1996 to
1999, the period during which the dark energy discovery was
made, Riess was a Miller Fellow at the
University of California, Berkeley. He has been a member of
the Johns Hopkins faculty since 2006.

"It is a tremendous honor to be elected to the
National Academy of Sciences. I am deeply
humbled," Riess said.